Visual-inertial tracking using rolling shutter cameras

ABSTRACT

Visual-inertial tracking of an eyewear device using a rolling shutter camera(s). The eyewear device includes a position determining system. Visual-inertial tracking is implemented by sensing motion of the eyewear device. An initial pose is obtained for a rolling shutter camera and an image of an environment is captured. The image includes feature points captured at a particular capture time. A number of poses for the rolling shutter camera is computed based on the initial pose and sensed movement of the device. The number of computed poses is responsive to the sensed movement of the mobile device. A computed pose is selected for each feature point in the image by matching the particular capture time for the feature point to the particular computed time for the computed pose. The position of the mobile device is determined within the environment using the feature points and the selected computed poses for the feature points.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.17/161,937 filed on Jan. 29, 2021, and claims priority to U.S.Provisional Application Ser. No. 63/045,568 filed on Jun. 29, 2020, thecontents of both of which are incorporated fully herein by reference.

TECHNICAL FIELD

Examples set forth in the present disclosure relate to visual-inertialtracking. More particularly, but not by way of limitation, the presentdisclosure describes methods and systems for computing poses for imagescaptured by rolling shutter cameras.

BACKGROUND

Rolling shutter cameras capture an image by rapidly scanning across ascene such that not all parts of the image are recorded at exactly thesame instant. Artefacts may arise if there is relative movement betweenthe camera and a scene during image acquisition.

BRIEF DESCRIPTION OF THE DRAWINGS

Features of the various implementations disclosed will be readilyunderstood from the following detailed description, in which referenceis made to the appending drawing figures. A reference numeral is usedwith each element in the description and throughout the several views ofthe drawing. When a plurality of similar elements is present, a singlereference numeral may be assigned to like elements, with an addedlower-case letter referring to a specific element.

The various elements shown in the figures are not drawn to scale unlessotherwise indicated. The dimensions of the various elements may beenlarged or reduced in the interest of clarity. The several figuresdepict one or more implementations and are presented by way of exampleonly and should not be construed as limiting. Included in the drawingare the following figures:

FIG. 1A is a side view (right) of an example hardware configuration ofan eyewear device suitable for use in a visual-inertial tracking system;

FIG. 1B is a perspective, partly sectional view of a right corner of theeyewear device of FIG. 1A depicting a right visible-light camera, and acircuit board;

FIG. 1C is a side view (left) of an example hardware configuration ofthe eyewear device of FIG. 1A, which shows a left visible-light camera;

FIG. 1D is a perspective, partly sectional view of a left corner of theeyewear device of FIG. 1C depicting the left visible-light camera, and acircuit board;

FIGS. 2A and 2B are rear views of example hardware configurations of aneyewear device utilized in the augmented reality production system;

FIG. 3 is a diagrammatic depiction of a three-dimensional scene, a leftraw image captured by a left visible-light camera, and a right raw imagecaptured by a right visible-light camera;

FIG. 4 is a functional block diagram of an example visual-inertialtracking system including a wearable device (e.g., an eyewear device)and a server system connected via various networks;

FIG. 5 is a diagrammatic representation of an example hardwareconfiguration for a mobile device of the augmented reality productionsystem of FIG. 4 ;

FIG. 6 is a schematic illustration of a user in an example environmentfor use in describing simultaneous localization and mapping;

FIG. 7 is a flow chart listing steps in an example method of displayingvirtual objects in a physical environment;

FIGS. 8A, 8B, 8C, and 8D are flow charts including steps of examplemethods of visual-inertial tracking with one or more rolling shuttercameras.

DETAILED DESCRIPTION

Various implementations and details are described with reference toexamples including a system for providing visual-inertial tracking of aneyewear device with a first rolling shutter camera. The eyewear deviceincludes a position determining system. Visual-inertial tracking isimplemented by sensing motion of the eyewear device and obtaining aninitial pose for the first rolling shutter camera, then capturing animage of an environment in which the image includes feature points. Themovement of the mobile device is captured with a motion detector and anumber of poses for the first rolling shutter camera are computed basedon the initial pose and the sensed movement wherein each computed posecorresponds to a particular computed time. A computed pose is selectedfor each feature point by matching the particular capture time for thefeature point to the particular computed time for the computed pose andthe position of the mobile device is determined within the environment.

The more poses that are calculated for each readout of a rolling shuttercamera generally improves the accuracy of the mobile device's estimatedpose within the environment and therefore improves the perceivedaugmented reality (AR) experience for the user when content is rendered.Each calculation of a pose, however, consumes processing resources. Insome situations (e.g., when the eyewear device is moving relativelyslowly), acceptable AR results may be achieved with fewer poses than ifthe eyewear device were moving faster. By adjusting the number of posescalculated responsive to movement of the eyewear device, processingresources can be conserved when they are not necessary to produceacceptable results.

The following detailed description includes systems, methods,techniques, instruction sequences, and computing machine programproducts illustrative of examples set forth in the disclosure. Numerousdetails and examples are included for the purpose of providing athorough understanding of the disclosed subject matter and its relevantteachings. Those skilled in the relevant art, however, may understandhow to apply the relevant teachings without such details. Aspects of thedisclosed subject matter are not limited to the specific devices,systems, and method described because the relevant teachings can beapplied or practice in a variety of ways. The terminology andnomenclature used herein is for the purpose of describing particularaspects only and is not intended to be limiting. In general, well-knowninstruction instances, protocols, structures, and techniques are notnecessarily shown in detail.

The term “coupled” or “connected” as used herein refers to any logical,optical, physical, or electrical connection, including a link or thelike by which the electrical or magnetic signals produced or supplied byone system element are imparted to another coupled or connected systemelement. Unless described otherwise, coupled or connected elements ordevices are not necessarily directly connected to one another and may beseparated by intermediate components, elements, or communication media,one or more of which may modify, manipulate, or carry the electricalsignals. The term “on” means directly supported by an element orindirectly supported by the element through another element integratedinto or supported by the element.

The orientations of the device and associated components and any othercomplete devices incorporating a camera, an inertial measurement unit,or both such as shown in any of the drawings, are given by way ofexample only, for illustration and discussion purposes. In operation,the eyewear device may be oriented in any other direction suitable tothe particular application of the eyewear device; for example, up, down,sideways, or any other orientation. Also, to the extent used herein, anydirectional term, such as front, rear, inward, outward, toward, left,right, lateral, longitudinal, up, down, upper, lower, top, bottom, side,horizontal, vertical, and diagonal are used by way of example only, andare not limiting as to the direction or orientation of any camera orinertial measurement unit as constructed as otherwise described herein.

Additional objects, advantages and novel features of the examples willbe set forth in part in the following description, and in part willbecome apparent to those skilled in the art upon examination of thefollowing and the accompanying drawings or may be learned by productionor operation of the examples. The objects and advantages of the presentsubject matter may be realized and attained by means of themethodologies, instrumentalities and combinations particularly pointedout in the appended claims.

Reference now is made in detail to the examples illustrated in theaccompanying drawings and discussed below.

FIG. 1A is a side view (right) of an example hardware configuration ofan eyewear device 100 which includes a touch-sensitive input device ortouchpad 181. As shown, the touchpad 181 may have a boundary that issubtle and not easily seen; alternatively, the boundary may be plainlyvisible or include a raised or otherwise tactile edge that providesfeedback to the user about the location and boundary of the touchpad181. In other implementations, the eyewear device 100 may include atouchpad on the left side.

The surface of the touchpad 181 is configured to detect finger touches,taps, and gestures (e.g., moving touches) for use with a GUI displayedby the eyewear device, on an image display, to allow the user tonavigate through and select menu options in an intuitive manner, whichenhances and simplifies the user experience.

Detection of finger inputs on the touchpad 181 can enable severalfunctions. For example, touching anywhere on the touchpad 181 may causethe GUI to display or highlight an item on the image display, which maybe projected onto at least one of the optical assemblies 180A, 180B.Double tapping on the touchpad 181 may select an item or icon. Slidingor swiping a finger in a particular direction (e.g., from front to back,back to front, up to down, or down to) may cause the items or icons toslide or scroll in a particular direction; for example, to move to anext item, icon, video, image, page, or slide. Sliding the finger inanother direction may slide or scroll in the opposite direction; forexample, to move to a previous item, icon, video, image, page, or slide.The touchpad 181 can be virtually anywhere on the eyewear device 100.

In one example, an identified finger gesture of a single tap on thetouchpad 181, initiates selection or pressing of a graphical userinterface element in the image presented on the image display of theoptical assembly 180A, 180B. An adjustment to the image presented on theimage display of the optical assembly 180A, 180B based on the identifiedfinger gesture can be a primary action which selects or submits thegraphical user interface element on the image display of the opticalassembly 180A, 180B for further display or execution.

As shown, the eyewear device 100 includes a right visible-light camera114B. As further described herein, two cameras 114A, 114B capture imageinformation for a scene from two separate viewpoints. The two capturedimages may be used to project a three-dimensional display onto an imagedisplay for viewing with 3D glasses.

The eyewear device 100 includes a right optical assembly 180B with animage display to present images, such as depth images. As shown in FIGS.1A and 1B, the eyewear device 100 includes the right visible-lightcamera 114B. The eyewear device 100 can include multiple visible-lightcameras 114A, 114B that form a passive type of three-dimensional camera,such as stereo camera, of which the right visible-light camera 114B islocated on a right corner 110B. As shown in FIGS. 1C-D, the eyeweardevice 100 also includes a left visible-light camera 114A.

Left and right visible-light cameras 114A, 114B are sensitive to thevisible-light range wavelength. Each of the visible-light cameras 114A,114B have a different frontward facing field of view which areoverlapping to enable generation of three-dimensional depth images, forexample, right visible-light camera 114B depicts a right field of view111B. Generally, a “field of view” is the part of the scene that isvisible through the camera at a particular position and orientation inspace. The fields of view 111A and 111B have an overlapping field ofview 304 (FIG. 3 ). Objects or object features outside the field of view111A, 111B when the visible-light camera captures the image are notrecorded in a raw image (e.g., photograph or picture). The field of viewdescribes an angle range or extent, which the image sensor of thevisible-light camera 114A, 114B picks up electromagnetic radiation of agiven scene in a captured image of the given scene. Field of view can beexpressed as the angular size of the view cone; i.e., an angle of view.The angle of view can be measured horizontally, vertically, ordiagonally.

In an example, visible-light cameras 114A, 114B have a field of viewwith an angle of view between 40° to 110°, for example approximately100°, and have a resolution of 480×480 pixels or greater. The “angle ofcoverage” describes the angle range that a lens of visible-light cameras114A, 114B or infrared camera 410 (see FIG. 2A) can effectively image.Typically, the camera lens produces an image circle that is large enoughto cover the film or sensor of the camera completely, possibly includingsome vignetting (e.g., a darkening of the image toward the edges whencompared to the center). If the angle of coverage of the camera lensdoes not fill the sensor, the image circle will be visible, typicallywith strong vignetting toward the edge, and the effective angle of viewwill be limited to the angle of coverage.

Examples of such visible-light cameras 114A, 114B include ahigh-resolution complementary metal-oxide-semiconductor (CMOS) imagesensor and a digital VGA camera (video graphics array) capable ofresolutions of 640p (e.g., 640×480 pixels for a total of 0.3megapixels), 720 p, or 1080 p. Other examples of visible-light cameras114A, 114B that can capture high-definition (HD) still images and storethem at a resolution of 1642 by 1642 pixels (or greater); or recordhigh-definition video at a high frame rate (e.g., thirty to sixty framesper second or more) and store the recording at a resolution of 1216 by1216 pixels (or greater).

The eyewear device 100 may capture image sensor data from thevisible-light cameras 114A, 114B along with geolocation data, digitizedby an image processor, for storage in a memory. The visible-lightcameras 114A, 114B capture respective left and right raw images in thetwo-dimensional space domain that comprise a matrix of pixels on atwo-dimensional coordinate system that includes an X-axis for horizontalposition and a Y-axis for vertical position. Each pixel includes a colorattribute value (e.g., a red pixel light value, a green pixel lightvalue, or a blue pixel light value); and a position attribute (e.g., anX-axis coordinate and a Y-axis coordinate).

In order to capture stereo images for later display as athree-dimensional projection, the image processor 412 (shown in FIG. 4 )may be coupled to the visible-light cameras 114A, 114B to receive andstore the visual image information. The image processor 412, or anotherprocessor, controls operation of the visible-light cameras 114A, 114B toact as a stereo camera simulating human binocular vision and may add atimestamp to each image. The timestamp on each pair of images allowsdisplay of the images together as part of a three-dimensionalprojection. Three-dimensional projections produce an immersive,life-like experience that is desirable in a variety of contexts,including virtual reality (VR) and video gaming.

FIG. 1B is a perspective, cross-sectional view of a right corner 110B ofthe eyewear device 100 of FIG. 1A depicting the right visible-lightcamera 114B of the camera system, and a circuit board. FIG. 1C is a sideview (left) of an example hardware configuration of an eyewear device100 of FIG. 1A, which shows a left visible-light camera 114A of thecamera system. FIG. 1D is a perspective, cross-sectional view of a leftcorner 110A of the eyewear device of FIG. 1C depicting the leftvisible-light camera 114A of the three-dimensional camera, and a circuitboard.

Construction and placement of the left visible-light camera 114A issubstantially similar to the right visible-light camera 114B, except theconnections and coupling are on the left lateral side 170A. As shown inthe example of FIG. 1B, the eyewear device 100 includes the rightvisible-light camera 114B and a circuit board 140B, which may be aflexible printed circuit board (PCB). The right hinge 126B connects theright corner 110B to a right temple 125B of the eyewear device 100. Insome examples, components of the right visible-light camera 114B, theflexible PCB 140B, or other electrical connectors or contacts may belocated on the right temple 125B or the right hinge 126B.

The right corner 110B includes corner body 190 and a corner cap, withthe corner cap omitted in the cross-section of FIG. 1B. Disposed insidethe right corner 110B are various interconnected circuit boards, such asPCBs or flexible PCBs, that include controller circuits for rightvisible-light camera 114B, microphone(s), low-power wireless circuitry(e.g., for wireless short range network communication via Bluetooth™),high-speed wireless circuitry (e.g., for wireless local area networkcommunication via Wi-Fi).

The right visible-light camera 114B is coupled to or disposed on theflexible PCB 140B and covered by a visible-light camera cover lens,which is aimed through opening(s) formed in the frame 105. For example,the right rim 107B of the frame 105, shown in FIG. 2A, is connected tothe right corner 110B and includes the opening(s) for the visible-lightcamera cover lens. The frame 105 includes a front side configured toface outward and away from the eye of the user. The opening for thevisible-light camera cover lens is formed on and through the front oroutward-facing side of the frame 105. In the example, the rightvisible-light camera 114B has an outward-facing field of view 111B(shown in FIG. 3 ) with a line of sight or perspective that iscorrelated with the right eye of the user of the eyewear device 100. Thevisible-light camera cover lens can also be adhered to a front side oroutward-facing surface of the right corner 110B in which an opening isformed with an outward-facing angle of coverage, but in a differentoutwardly direction. The coupling can also be indirect via interveningcomponents.

As shown in FIG. 1B, flexible PCB 140B is disposed inside the rightcorner 110B and is coupled to one or more other components housed in theright corner 110B. Although shown as being formed on the circuit boardsof the right corner 110B, the right visible-light camera 114B can beformed on the circuit boards of the left corner 110A, the temples 125A,125B, or the frame 105.

FIGS. 2A and 2B are perspective views, from the rear, of examplehardware configurations of the eyewear device 100, including twodifferent types of image displays. The eyewear device 100 is sized andshaped in a form configured for wearing by a user; the form ofeyeglasses is shown in the example. The eyewear device 100 can takeother forms and may incorporate other types of frameworks; for example,a headgear, a headset, or a helmet.

In the eyeglasses example, eyewear device 100 includes a frame 105including a left rim 107A connected to a right rim 107B via a bridge 106adapted to be supported by a nose of the user. The left and right rims107A, 107B include respective apertures 175A, 175B, which hold arespective optical element 180A, 180B, such as a lens and a displaydevice. As used herein, the term “lens” is meant to include transparentor translucent pieces of glass or plastic having curved or flat surfacesthat cause light to converge/diverge or that cause little or noconvergence or divergence.

Although shown as having two optical elements 180A, 180B, the eyeweardevice 100 can include other arrangements, such as a single opticalelement (or it may not include any optical element 180A, 180B),depending on the application or the intended user of the eyewear device100. As further shown, eyewear device 100 includes a left corner 110Aadjacent the left lateral side 170A of the frame 105 and a right corner110B adjacent the right lateral side 170B of the frame 105. The corners110A, 110B may be integrated into the frame 105 on the respective sides170A, 170B (as illustrated) or implemented as separate componentsattached to the frame 105 on the respective sides 170A, 170B.Alternatively, the corners 110A, 110B may be integrated into temples(not shown) attached to the frame 105.

In one example, the image display of optical assembly 180A, 180Bincludes an integrated image display. As shown in FIG. 2A, each opticalassembly 180A, 180B includes a suitable display matrix 177, such as aliquid crystal display (LCD), an organic light-emitting diode (OLED)display, or any other such display. Each optical assembly 180A, 180Balso includes an optical layer or layers 176, which can include lenses,optical coatings, prisms, mirrors, waveguides, optical strips, and otheroptical components in any combination. The optical layers 176A, 176B, .. . 176N (shown as 176A-N in FIG. 2A and herein) can include a prismhaving a suitable size and configuration and including a first surfacefor receiving light from a display matrix and a second surface foremitting light to the eye of the user. The prism of the optical layers176A-N extends over all or at least a portion of the respectiveapertures 175A, 175B formed in the left and right rims 107A, 107B topermit the user to see the second surface of the prism when the eye ofthe user is viewing through the corresponding left and right rims 107A,107B. The first surface of the prism of the optical layers 176A-N facesupwardly from the frame 105 and the display matrix 177 overlies theprism so that photons and light emitted by the display matrix 177impinge the first surface. The prism is sized and shaped so that thelight is refracted within the prism and is directed toward the eye ofthe user by the second surface of the prism of the optical layers176A-N. In this regard, the second surface of the prism of the opticallayers 176A-N can be convex to direct the light toward the center of theeye. The prism can optionally be sized and shaped to magnify the imageprojected by the display matrix 177, and the light travels through theprism so that the image viewed from the second surface is larger in oneor more dimensions than the image emitted from the display matrix 177.

In one example, the optical layers 176A-N may include an LCD layer thatis transparent (keeping the lens open) unless and until a voltage isapplied which makes the layer opaque (closing or blocking the lens). Theimage processor 412 on the eyewear device 100 may execute programming toapply the voltage to the LCD layer in order to produce an active shuttersystem, making the eyewear device 100 suitable for viewing visualcontent when displayed as a three-dimensional projection. Technologiesother than LCD may be used for the active shutter mode, including othertypes of reactive layers that are responsive to a voltage or anothertype of input.

In another example, the image display device of optical assembly 180A,180B includes a projection image display as shown in FIG. 2B. Eachoptical assembly 180A, 180B includes a laser projector 150, which is athree-color laser projector using a scanning mirror or galvanometer.During operation, an optical source such as a laser projector 150 isdisposed in or on one of the temples 125A, 125B of the eyewear device100. Optical assembly 180B in this example includes one or more opticalstrips 155A, 155B, . . . 155N (shown as 155A-N in FIG. 2B) which arespaced apart and across the width of the lens of each optical assembly180A, 180B or across a depth of the lens between the front surface andthe rear surface of the lens.

As the photons projected by the laser projector 150 travel across thelens of each optical assembly 180A, 180B, the photons encounter theoptical strips 155A-N. When a particular photon encounters a particularoptical strip, the photon is either redirected toward the user's eye, orit passes to the next optical strip. A combination of modulation oflaser projector 150, and modulation of optical strips, may controlspecific photons or beams of light. In an example, a processor controlsoptical strips 155A-N by initiating mechanical, acoustic, orelectromagnetic signals. Although shown as having two optical assemblies180A, 180B, the eyewear device 100 can include other arrangements, suchas a single or three optical assemblies, or each optical assembly 180A,180B may have arranged different arrangement depending on theapplication or intended user of the eyewear device 100.

As further shown in FIGS. 2A and 2B, eyewear device 100 includes a leftcorner 110A adjacent the left lateral side 170A of the frame 105 and aright corner 110B adjacent the right lateral side 170B of the frame 105.The corners 110A, 110B may be integrated into the frame 105 on therespective lateral sides 170A, 170B (as illustrated) or implemented asseparate components attached to the frame 105 on the respective sides170A, 170B. Alternatively, the corners 110A, 110B may be integrated intotemples 125A, 125B attached to the frame 105.

In another example, the eyewear device 100 shown in FIG. 2B may includetwo projectors, a left projector 150A (not shown) and a right projector150B (shown as projector 150). The left optical assembly 180A mayinclude a left display matrix 177A (not shown) or a left set of opticalstrips 155′A, 155′B, . . . 155′N (155 prime, A through N, not shown)which are configured to interact with light from the left projector150A. Similarly, the right optical assembly 180B may include a rightdisplay matrix 177B (not shown) or a right set of optical strips 155″A,155″B, . . . 155″N (155 double prime, A through N, not shown) which areconfigured to interact with light from the right projector 150B. In thisexample, the eyewear device 100 includes a left display and a rightdisplay.

FIG. 3 is a diagrammatic depiction of a three-dimensional scene 306, aleft raw image 302A captured by a left visible-light camera 114A, and aright raw image 302B captured by a right visible-light camera 114B. Theleft field of view 111A may overlap, as shown, with the right field ofview 111B. The overlapping field of view 304 represents that portion ofthe image captured by both cameras 114A, 114B. The term ‘overlapping’when referring to field of view means the matrix of pixels in thegenerated raw images overlap by thirty percent (30%) or more.‘Substantially overlapping’ means the matrix of pixels in the generatedraw images—or in the infrared image of scene—overlap by fifty percent(50%) or more. As described herein, the two raw images 302A, 302B may beprocessed to include a timestamp, which allows the images to bedisplayed together as part of a three-dimensional projection.

For the capture of stereo images, as illustrated in FIG. 3 , a pair ofraw red, green, and blue (RGB) images are captured of a real scene 306at a given moment in time—a left raw image 302A captured by the leftcamera 114A and right raw image 302B captured by the right camera 114B.When the pair of raw images 302A, 302B are processed (e.g., by the imageprocessor 412), depth images are generated. The generated depth imagesmay be viewed on an optical assembly 180A, 180B of an eyewear device, onanother display (e.g., the image display 580 on a mobile device 401), oron a screen.

The generated depth images are in the three-dimensional space domain andcan comprise a matrix of vertices on a three-dimensional locationcoordinate system that includes an X axis for horizontal position (e.g.,length), a Y axis for vertical position (e.g., height), and a Z axis fordepth (e.g., distance). Each vertex may include a color attribute (e.g.,a red pixel light value, a green pixel light value, or a blue pixellight value); a position attribute (e.g., an X location coordinate, a Ylocation coordinate, and a Z location coordinate); a texture attribute;a reflectance attribute; or a combination thereof. The texture attributequantifies the perceived texture of the depth image, such as the spatialarrangement of color or intensities in a region of vertices of the depthimage.

In one example, the interactive augmented reality system 400 (FIG. 4 )includes the eyewear device 100, which includes a frame 105 and a lefttemple 110A extending from a left lateral side 170A of the frame 105 anda right temple 125B extending from a right lateral side 170B of theframe 105. The eyewear device 100 may further include at least twovisible-light cameras 114A, 114B having overlapping fields of view. Inone example, the eyewear device 100 includes a left visible-light camera114A with a left field of view 111A, as illustrated in FIG. 3 . The leftcamera 114A is connected to the frame 105 or the left temple 110A tocapture a left raw image 302A from the left side of scene 306. Theeyewear device 100 further includes a right visible-light camera 114Bwith a right field of view 111B. The right camera 114B is connected tothe frame 105 or the right temple 125B to capture a right raw image 302Bfrom the right side of scene 306.

FIG. 4 is a functional block diagram of an example interactive augmentedreality system 400 that includes a wearable device (e.g., an eyeweardevice 100), a mobile device 401, and a server system 498 connected viavarious networks 495 such as the Internet. The interactive augmentedreality system 400 includes a low-power wireless connection 425 and ahigh-speed wireless connection 437 between the eyewear device 100 andthe mobile device 401.

As shown in FIG. 4 , the eyewear device 100 includes one or morevisible-light cameras 114A, 114B that capture still images, videoimages, or both still and video images, as described herein. The cameras114A, 114B may have a direct memory access (DMA) to high-speed circuitry430 and function as a stereo camera. The cameras 114A, 114B may be usedto capture initial-depth images that may be rendered intothree-dimensional (3D) models that are texture-mapped images of a red,green, and blue (RGB) imaged scene. The device 100 may also include adepth sensor 213, which uses infrared signals to estimate the positionof objects relative to the device 100. The depth sensor 213 in someexamples includes one or more infrared emitter(s) 215 and infraredcamera(s) 410.

The eyewear device 100 further includes two image displays of eachoptical assembly 180A, 180B (one associated with the left side 170A andone associated with the right side 170B). The eyewear device 100 alsoincludes an image display driver 442, an image processor 412, low-powercircuitry 420, and high-speed circuitry 430. The image displays of eachoptical assembly 180A, 180B are for presenting images, including stillimages, video images, or still and video images. The image displaydriver 442 is coupled to the image displays of each optical assembly180A, 180B in order to control the display of images.

The eyewear device 100 additionally includes one or more speakers 440(e.g., one associated with the left side of the eyewear device andanother associated with the right side of the eyewear device). Thespeakers 440 may be incorporated into the frame 105, temples 125, orcorners 110 of the eyewear device 100. The one or more speakers 440 aredriven by audio processor 443 under control of low-power circuitry 420,high-speed circuitry 430, or both. The speakers 440 are for presentingaudio signals including, for example, a beat track. The audio processor443 is coupled to the speakers 440 in order to control the presentationof sound.

The components shown in FIG. 4 for the eyewear device 100 are located onone or more circuit boards, for example a printed circuit board (PCB) orflexible printed circuit (FPC), located in the rims or temples.Alternatively, or additionally, the depicted components can be locatedin the corners, frames, hinges, or bridge of the eyewear device 100.Left and right visible-light cameras 114A, 114B can include digitalcamera elements such as a complementary metal-oxide-semiconductor (CMOS)image sensor, a charge-coupled device, a lens, or any other respectivevisible or light capturing elements that may be used to capture data,including still images or video of scenes with unknown objects.

As shown in FIG. 4 , high-speed circuitry 430 includes a high-speedprocessor 432, a memory 434, and high-speed wireless circuitry 436. Inthe example, the image display driver 442 is coupled to the high-speedcircuitry 430 and operated by the high-speed processor 432 in order todrive the left and right image displays of each optical assembly 180A,180B. High-speed processor 432 may be any processor capable of managinghigh-speed communications and operation of any general computing systemneeded for eyewear device 100. High-speed processor 432 includesprocessing resources needed for managing high-speed data transfers onhigh-speed wireless connection 437 to a wireless local area network(WLAN) using high-speed wireless circuitry 436.

In some examples, the high-speed processor 432 executes an operatingsystem such as a LINUX operating system or other such operating systemof the eyewear device 100 and the operating system is stored in memory434 for execution. In addition to any other responsibilities, thehigh-speed processor 432 executes a software architecture for theeyewear device 100 that is used to manage data transfers with high-speedwireless circuitry 436. In some examples, high-speed wireless circuitry436 is configured to implement Institute of Electrical and ElectronicEngineers (IEEE) 802.11 communication standards, also referred to hereinas Wi-Fi. In other examples, other high-speed communications standardsmay be implemented by high-speed wireless circuitry 436.

The low-power circuitry 420 includes a low-power processor 422 andlow-power wireless circuitry 424. The low-power wireless circuitry 424and the high-speed wireless circuitry 436 of the eyewear device 100 caninclude short-range transceivers (Bluetooth™ or Bluetooth Low-Energy(BLE)) and wireless wide, local, or wide-area network transceivers(e.g., cellular or Wi-Fi). Mobile device 401, including the transceiverscommunicating via the low-power wireless connection 425 and thehigh-speed wireless connection 437, may be implemented using details ofthe architecture of the eyewear device 100, as can other elements of thenetwork 495.

Memory 434 includes any storage device capable of storing various dataand applications, including, among other things, camera data generatedby the left and right visible-light cameras 114A, 114B, the infraredcamera(s) 410, the image processor 412, and images generated for displayby the image display driver 442 on the image display of each opticalassembly 180A, 180B. Although the memory 434 is shown as integrated withhigh-speed circuitry 430, the memory 434 in other examples may be anindependent, standalone element of the eyewear device 100. In certainsuch examples, electrical routing lines may provide a connection througha chip that includes the high-speed processor 432 from the imageprocessor 412 or low-power processor 422 to the memory 434. In otherexamples, the high-speed processor 432 may manage addressing of memory434 such that the low-power processor 422 will boot the high-speedprocessor 432 any time that a read or write operation involving memory434 is needed.

As shown in FIG. 4 , the high-speed processor 432 of the eyewear device100 can be coupled to the camera system (visible-light cameras 114A,114B), the image display driver 442, the user input device 491, and thememory 434. As shown in FIG. 5 , the CPU 540 of the mobile device 401may be coupled to a camera system 570, a mobile display driver 582, auser input layer 591, and a memory 540A.

The server system 498 may be one or more computing devices as part of aservice or network computing system, for example, that include aprocessor, a memory, and network communication interface to communicateover the network 495 with an eyewear device 100 and a mobile device 401.

The output components of the eyewear device 100 include visual elements,such as the left and right image displays associated with each lens oroptical assembly 180A, 180B as described in FIGS. 2A and 2B (e.g., adisplay such as a liquid crystal display (LCD), a plasma display panel(PDP), a light emitting diode (LED) display, a projector, or awaveguide). The eyewear device 100 may include a user-facing indicator(e.g., an LED, a loudspeaker, or a vibrating actuator), or anoutward-facing signal (e.g., an LED, a loudspeaker). The image displaysof each optical assembly 180A, 180B are driven by the image displaydriver 442. In some example configurations, the output components of theeyewear device 100 further include additional indicators such as audibleelements (e.g., loudspeakers), tactile components (e.g., an actuatorsuch as a vibratory motor to generate haptic feedback), and other signalgenerators. For example, the device 100 may include a user-facing set ofindicators, and an outward-facing set of signals. The user-facing set ofindicators are configured to be seen or otherwise sensed by the user ofthe device 100. For example, the device 100 may include an LED displaypositioned so the user can see it, a one or more speakers positioned togenerate a sound the user can hear, or an actuator to provide hapticfeedback the user can feel. The outward-facing set of signals areconfigured to be seen or otherwise sensed by an observer near the device100. Similarly, the device 100 may include an LED, a loudspeaker, or anactuator that is configured and positioned to be sensed by an observer.

The input components of the eyewear device 100 may include alphanumericinput components (e.g., a touch screen or touchpad configured to receivealphanumeric input, a photo-optical keyboard, or otheralphanumeric-configured elements), pointer-based input components (e.g.,a mouse, a touchpad, a trackball, a joystick, a motion sensor, or otherpointing instruments), tactile input components (e.g., a button switch,a touch screen or touchpad that senses the location, force or locationand force of touches or touch gestures, or other tactile-configuredelements), and audio input components (e.g., a microphone), and thelike. The mobile device 401 and the server system 498 may includealphanumeric, pointer-based, tactile, audio, and other input components.

In some examples, the eyewear device 100 includes a collection ofmotion-sensing components referred to as an inertial measurement unit472. The motion-sensing components may be micro-electro-mechanicalsystems (MEMS) with microscopic moving parts, often small enough to bepart of a microchip. The inertial measurement unit (IMU) 472 in someexample configurations includes an accelerometer, a gyroscope, and amagnetometer. The accelerometer senses the linear acceleration of thedevice 100 (including the acceleration due to gravity) relative to threeorthogonal axes (x, y, z). The gyroscope senses the angular velocity ofthe device 100 about three axes of rotation (pitch, roll, yaw).Together, the accelerometer and gyroscope can provide position,orientation, and motion data about the device relative to six axes (x,y, z, pitch, roll, yaw). The magnetometer, if present, senses theheading of the device 100 relative to magnetic north. The position ofthe device 100 may be determined by location sensors, such as a GPS unit473, one or more transceivers to generate relative position coordinates,altitude sensors or barometers, and other orientation sensors. Suchpositioning system coordinates can also be received over the wirelessconnections 425, 437 from the mobile device 401 via the low-powerwireless circuitry 424 or the high-speed wireless circuitry 436.

The IMU 472 may include or cooperate with a digital motion processor orprogramming that gathers the raw data from the components and computes anumber of useful values about the position, orientation, and motion ofthe device 100. For example, the acceleration data gathered from theaccelerometer can be integrated to obtain the velocity relative to eachaxis (x, y, z); and integrated again to obtain the position of thedevice 100 (in linear coordinates, x, y, and z). The angular velocitydata from the gyroscope can be integrated to obtain the position of thedevice 100 (in spherical coordinates). The programming for computingthese useful values may be stored in memory 434 and executed by thehigh-speed processor 432 of the eyewear device 100.

The eyewear device 100 may optionally include additional peripheralsensors, such as biometric sensors, specialty sensors, or displayelements integrated with eyewear device 100. For example, peripheraldevice elements may include any I/O components including outputcomponents, motion components, position components, or any other suchelements described herein. For example, the biometric sensors mayinclude components to detect expressions (e.g., hand expressions, facialexpressions, vocal expressions, body gestures, or eye tracking), tomeasure bio signals (e.g., blood pressure, heart rate, body temperature,perspiration, or brain waves), or to identify a person (e.g.,identification based on voice, retina, facial characteristics,fingerprints, or electrical bio signals such as electroencephalogramdata), and the like.

The mobile device 401 may be a smartphone, tablet, laptop computer,access point, or any other such device capable of connecting witheyewear device 100 using both a low-power wireless connection 425 and ahigh-speed wireless connection 437. Mobile device 401 is connected toserver system 498 and network 495. The network 495 may include anycombination of wired and wireless connections.

The interactive augmented reality system 400, as shown in FIG. 4 ,includes a computing device, such as mobile device 401, coupled to aneyewear device 100 over a network. The interactive augmented realitysystem 400 includes a memory for storing instructions and a processorfor executing the instructions. Execution of the instructions of theinteractive augmented reality system 400 by the processor 432 configuresthe eyewear device 100 to cooperate with the mobile device 401. Theinteractive augmented reality system 400 may utilize the memory 434 ofthe eyewear device 100 or the memory elements 540A, 540B, 540C of themobile device 401 (FIG. 5 ). Also, the interactive augmented realitysystem 400 may utilize the processor elements 432, 422 of the eyeweardevice 100 or the central processing unit (CPU) 540 of the mobile device401 (FIG. 5 ). In addition, the interactive augmented reality system 400may further utilize the memory and processor elements of the serversystem 498. In this aspect, the memory and processing functions of theinteractive augmented reality system 400 can be shared or distributedacross the eyewear device 100, the mobile device 401, and the serversystem 498.

The memory 434 includes song files 482 and virtual objects 484. The songfiles 482 includes a tempo (e.g., beat track) and, optionally, asequence of notes and note values. A note is a symbol denoting aparticular pitch or other musical sound. The note value includes theduration the note is played, relative to the tempo, and may includeother qualities such as loudness, emphasis, articulation, and phrasingrelative to other notes. The tempo, in some implementations, includes adefault value along with a user interface through which the user mayselect a particular tempo for use during playback of the song. Thevirtual objects 484 include image data for identifying objects orfeatures in images captured by the cameras 114. The objects may bephysical features such as known paintings or physical markers for use inlocalizing the eyewear device 100 within an environment.

The memory 434 additionally includes, for execution by the processor432, a position detection utility 460, a marker registration utility462, a localization utility 464, a virtual object rendering utility 466,a physics engine 468, and a prediction engine 470. The positiondetection utility 460 configures the processor 432 to determine theposition (location and orientation) within an environment, e.g., usingthe localization utility 464. The marker registration utility 462configures the processor 432 to register markers within the environment.The markers may be predefined physical markers having a known locationwithin an environment or assigned by the processor 432 to a particularlocation with respect to the environment within which the eyewear device100 is operating or with respect to the eyewear itself. The localizationutility 464 configures the processor 432 to obtain localization data foruse in determining the position of the eyewear device 100, virtualobjects presented by the eyewear device, or a combination thereof. Thelocation data may be derived from a series of images, an IMU unit 472, aGPS unit 473, or a combination thereof. The virtual object renderingutility 466 configures the processor 432 to render virtual images fordisplay by the image display 180 under control of the image displaydriver 442 and the image processor 412. The physics engine 468configures the processor 432 to apply laws of physics such as gravityand friction to the virtual word, e.g., between virtual game pieces. Theprediction engine 470 configures the processor 432 to predictanticipated movement of an object such as the eyewear device 100 basedon its current heading, input from sensors such as the IMU 472, imagesof the environment, or a combination thereof.

FIG. 5 is a high-level functional block diagram of an example mobiledevice 401. Mobile device 401 includes a flash memory 540A which storesprogramming to be executed by the CPU 540 to perform all or a subset ofthe functions described herein.

The mobile device 401 may include a camera 570 that comprises at leasttwo visible-light cameras (first and second visible-light cameras withoverlapping fields of view) or at least one visible-light camera and adepth sensor with substantially overlapping fields of view. Flash memory540A may further include multiple images or video, which are generatedvia the camera 570.

As shown, the mobile device 401 includes an image display 580, a mobiledisplay driver 582 to control the image display 580, and a displaycontroller 584. In the example of FIG. 5 , the image display 580includes a user input layer 591 (e.g., a touchscreen) that is layered ontop of or otherwise integrated into the screen used by the image display580.

Examples of touchscreen-type mobile devices that may be used include(but are not limited to) a smart phone, a personal digital assistant(PDA), a tablet computer, a laptop computer, or other portable device.However, the structure and operation of the touchscreen-type devices isprovided by way of example; the subject technology as described hereinis not intended to be limited thereto. For purposes of this discussion,FIG. 5 therefore provides a block diagram illustration of the examplemobile device 401 with a user interface that includes a touchscreeninput layer 591 for receiving input (by touch, multi-touch, or gesture,and the like, by hand, stylus, or other tool) and an image display 580for displaying content

As shown in FIG. 5 , the mobile device 401 includes at least one digitaltransceiver (XCVR) 510, shown as WWAN XCVRs, for digital wirelesscommunications via a wide-area wireless mobile communication network.The mobile device 401 also includes additional digital or analogtransceivers, such as short-range transceivers (XCVRs) 520 forshort-range network communication, such as via NFC, VLC, DECT, ZigBee,Bluetooth™, or Wi-Fi. For example, short range XCVRs 520 may take theform of any available two-way wireless local area network (WLAN)transceiver of a type that is compatible with one or more standardprotocols of communication implemented in wireless local area networks,such as one of the Wi-Fi standards under IEEE 802.11.

To generate location coordinates for positioning of the mobile device401, the mobile device 401 can include a global positioning system (GPS)receiver. Alternatively, or additionally the mobile device 401 canutilize either or both the short range XCVRs 520 and WWAN XCVRs 510 forgenerating location coordinates for positioning. For example, cellularnetwork, Wi-Fi, or Bluetooth™ based positioning systems can generatevery accurate location coordinates, particularly when used incombination. Such location coordinates can be transmitted to the eyeweardevice over one or more network connections via XCVRs 510, 520.

The transceivers 510, 520 (i.e., the network communication interface)conforms to one or more of the various digital wireless communicationstandards utilized by modern mobile networks. Examples of WWANtransceivers 510 include (but are not limited to) transceiversconfigured to operate in accordance with Code Division Multiple Access(CDMA) and 3rd Generation Partnership Project (3GPP) networktechnologies including, for example and without limitation, 3GPP type 2(or 3GPP2) and LTE, at times referred to as “4G.” For example, thetransceivers 510, 520 provide two-way wireless communication ofinformation including digitized audio signals, still image and videosignals, web page information for display as well as web-related inputs,and various types of mobile message communications to/from the mobiledevice 401.

The mobile device 401 further includes a microprocessor that functionsas a central processing unit (CPU); shown as CPU 540 in FIG. 4 . Aprocessor is a circuit having elements structured and arranged toperform one or more processing functions, typically various dataprocessing functions. Although discrete logic components could be used,the examples utilize components forming a programmable CPU. Amicroprocessor for example includes one or more integrated circuit (IC)chips incorporating the electronic elements to perform the functions ofthe CPU. The CPU 540, for example, may be based on any known oravailable microprocessor architecture, such as a Reduced Instruction SetComputing (RISC) using an ARM architecture, as commonly used today inmobile devices and other portable electronic devices. Of course, otherarrangements of processor circuitry may be used to form the CPU 540 orprocessor hardware in smartphone, laptop computer, and tablet.

The CPU 540 serves as a programmable host controller for the mobiledevice 401 by configuring the mobile device 401 to perform variousoperations, for example, in accordance with instructions or programmingexecutable by CPU 540. For example, such operations may include variousgeneral operations of the mobile device, as well as operations relatedto the programming for applications on the mobile device. Although aprocessor may be configured by use of hardwired logic, typicalprocessors in mobile devices are general processing circuits configuredby execution of programming.

The mobile device 401 includes a memory or storage system, for storingprogramming and data. In the example, the memory system may include aflash memory 540A, a random-access memory (RAM) 540B, and other memorycomponents 540C, as needed. The RAM 540B serves as short-term storagefor instructions and data being handled by the CPU 540, e.g., as aworking data processing memory. The flash memory 540A typically provideslonger-term storage.

Hence, in the example of mobile device 401, the flash memory 540A isused to store programming or instructions for execution by the CPU 540.Depending on the type of device, the mobile device 401 stores and runs amobile operating system through which specific applications areexecuted. Examples of mobile operating systems include Google Android,Apple iOS (for iPhone or iPad devices), Windows Mobile, Amazon Fire OS,RIM BlackBerry OS, or the like.

The processor 432 within the eyewear device 100 constructs a map of theenvironment surrounding the eyewear device 100, determines a location ofthe eyewear device within the mapped environment, and determines arelative position of the eyewear device to one or more objects in themapped environment. In one example, the processor 432 constructs the mapand determines location and position information using a simultaneouslocalization and mapping (SLAM) algorithm applied to data received fromone or more sensors. In the context of augmented reality, a SLAMalgorithm is used to construct and update a map of an environment, whilesimultaneously tracking and updating the location of a device (or auser) within the mapped environment. The mathematical solution can beapproximated using various statistical methods, such as particlefilters, Kalman filters, extended Kalman filters, and covarianceintersection.

Sensor data includes images received from one or both of the cameras114A, 114B, distance(s) received from a laser range finder, positioninformation received from a GPS unit 473, or a combination of two ormore of such sensor data, or from other sensors providing data useful indetermining positional information.

FIG. 6 depicts an example environment 600 along with elements that areuseful for natural feature tracking (NFT; e.g., a tracking applicationusing a SLAM algorithm). A user 602 of the eyewear device 100 is presentin an example physical environment 600 (which, in FIG. 6 , is aninterior room). The processor 432 of the eyewear device 100 determinesits position with respect to one or more objects 604 within theenvironment 600 using captured images, constructs a map of theenvironment 600 using a coordinate system (x, y, z) for the environment600, and determines its position within the coordinate system.Additionally, the processor 432 determines a head pose (roll, pitch, andyaw) of the eyewear device 100 within the environment by using two ormore location points (e.g., three location points 606 a, 606 b, and 606c) associated with a single object 604 a, or by using one or morelocation points 606 associated with two or more objects 604 a, 604 b,604 c. In one example, the processor 432 of the eyewear device 100positions a virtual object 408 (such as the key shown in FIG. 6 ) withinthe environment 600 for augmented reality viewing via image displays180.

FIG. 7 is a flow chart 700 depicting a method for visual-inertialtracking on a wearable device (e.g., an eyewear device) having a firstrolling shutter camera described herein. Although the steps aredescribed with reference to the eyewear device 100, as described herein,other implementations of the steps described, for other types ofdevices, will be understood by one of skill in the art from thedescription herein. Additionally, it is contemplated that one or more ofthe steps shown in FIG. 7 , and in other figures, and described hereinmay be omitted, performed simultaneously or in a series, performed in anorder other than illustrated and described, or performed in conjunctionwith additional steps.

At block 702, the eyewear device 100 captures one or more input imagesof a physical environment 600 near the eyewear device 100. The processor432 may continuously receive input images from the visible lightcamera(s) 114 and store those images in memory 434 for processing.Additionally, the eyewear device 100 may capture information from othersensors (e.g., location information from a GPS unit 473, orientationinformation from an IMU 472, or distance information from a depthsensor).

At block 704, the eyewear device 100 compares objects in the capturedimages to objects stored in a library of images to identify a match. Insome implementations, the processor 432 stores the captured images inmemory 434. A library of images of known objects is stored in a virtualobject database 484.

In one example, the processor 432 is programmed to identify a predefinedparticular object (e.g., a particular picture 604 a hanging in a knownlocation on a wall, a window 604 b in another wall, or an object such asa safe 604 c positioned on the floor). Other sensor data, such as GPSdata, may be used to narrow down the number of known objects for use inthe comparison (e.g., only images associated with a room identifiedthrough GPS coordinates). In another example, the processor 432 isprogrammed to identify predefined general objects (such as one or moretrees within a park).

At block 706, the eyewear device 100 determines its position withrespect to the object(s). The processor 432 may determine its positionwith respect to the objects by comparing and processing distancesbetween two or more points in the captured images (e.g., between two ormore location points on one objects 604 or between a location point 606on each of two objects 604) to known distances between correspondingpoints in the identified objects. Distances between the points of thecaptured images greater than the points of the identified objectsindicates the eyewear device 100 is closer to the identified object thanthe imager that captured the image including the identified object. Onthe other hand, distances between the points of the captured images lessthan the points of the identified objects indicates the eyewear device100 is further from the identified object than the imager that capturedthe image including the identified object. By processing the relativedistances, the processor 432 is able to determine the position withrespect to the objects(s). Alternatively, or additionally, other sensorinformation, such as laser distance sensor information, may be used todetermine position with respect to the object(s).

At block 708, the eyewear device 100 constructs a map of an environment600 surrounding the eyewear device 100 and determines its locationwithin the environment. In one example, where the identified object(block 704) has a predefined coordinate system (x, y, z), the processor432 of the eyewear device 100 constructs the map using that predefinedcoordinate system and determines its position within that coordinatesystem based on the determined positions (block 706) with respect to theidentified objects. In another example, the eyewear device constructs amap using images of permanent or semi-permanent objects 604 within anenvironment (e.g., a tree or a park bench within a park). In accordancewith this example, the eyewear device 100 may define the coordinatesystem (x′, y′, z′) used for the environment.

At block 710, the eyewear device 100 determines a head pose (roll,pitch, and yaw) of the eyewear device 100 within the environment. Theprocessor 432 determines head pose by using two or more location points(e.g., three location points 606 a, 606 b, and 606 c) on one or moreobjects 604 or by using one or more location points 606 on two or moreobjects 604. Using conventional image processing algorithms, theprocessor 432 determines roll, pitch, and yaw by comparing the angle andlength of a line extending between the location points for the capturedimages and the known images.

At block 712, the eyewear device 100 presents visual images to the user.The processor 432 presents images to the user on the image displays 180using the image processor 412 and the image display driver 442. Theprocessor develops and presents the visual images via the image displaysresponsive to the location of the eyewear device 100 within theenvironment 600.

At block 714, the steps described above with reference to blocks 706-712are repeated to update the position of the eyewear device 100 and whatis viewed by the user 602 as the user moves through the environment 600.

Referring again to FIG. 6 , the method of implementing augmented realityvirtual guidance applications described herein, in this example,includes virtual markers (e.g., virtual marker 610 a) associated withphysical objects (e.g., painting 604 a) and virtual markers associatedwith virtual objects (e.g., key 608). In one example, an eyewear device100 uses the markers associated with physical objects to determine theposition of the eyewear device 100 within an environment and uses themarkers associated with virtual objects to generate overlay imagespresenting the associated virtual object(s) 608 in the environment 600at the virtual marker position on the display of the eyewear device 100.For example, markers are registered at locations in the environment foruse in tracking and updating the location of users, devices, and objects(virtual and physical) in a mapped environment. Markers are sometimesregistered to a high-contrast physical object, such as the relativelydark object 604 a mounted on a lighter-colored wall, to assist camerasand other sensors with the task of detecting the marker. The markers maybe preassigned or may be assigned by the eyewear device 100 uponentering the environment. Markers are also registered at locations inthe environment for use in presenting virtual images at those locationsin the mapped environment.

Markers can be encoded with or otherwise linked to information. A markermight include position information, a physical code (such as a bar codeor a QR code; either visible to the user or hidden), or a combinationthereof. A set of data associated with the marker is stored in thememory 434 of the eyewear device 100. The set of data includesinformation about the marker 610a, the marker's position (location andorientation), one or more virtual objects, or a combination thereof. Themarker position may include three-dimensional coordinates for one ormore marker landmarks 616 a, such as the corner of the generallyrectangular marker 610 a shown in FIG. 6 . The marker location may beexpressed relative to real-world geographic coordinates, a system ofmarker coordinates, a position of the eyewear device 100, or othercoordinate system. The one or more virtual objects associated with themarker 610 a may include any of a variety of material, including stillimages, video, audio, tactile feedback, executable applications,interactive user interfaces and experiences, and combinations orsequences of such material. Any type of content capable of being storedin a memory and retrieved when the marker 610 a is encountered orassociated with an assigned marker may be classified as a virtual objectin this context. The key 608 shown in FIG. 6 , for example, is a virtualobject displayed as a still image, either 2D or 3D, at a markerlocation.

In one example, the marker 610 a may be registered in memory as beinglocated near and associated with a physical object 604 a (e.g., theframed work of art shown in FIG. 6 ). In another example, the marker maybe registered in memory as being a particular position with respect tothe eyewear device 100.

FIG. 8A is a flow chart 800 depicting a method for visual-inertialtracking on eyewear device 100 that uses a camera system comprising afirst rolling shutter camera. At block 802, the eyewear device 100obtains an initial head pose for the first rolling shutter camera bydetermining head pose (roll, pitch, and yaw) of the eyewear device 100within the environment. In some examples the pose is stored by processor432 in memory, e.g., memory 434. In one example, the processor 432stores the pose in a look-up table in memory 434. The processor 432 mayset up the look-up table in memory and maintain the look-up table duringa visual-inertial tracking process by eyewear device 100. The look-uptable includes an entry corresponding to each line of an image capturedby at least one rolling shutter camera (or, for example, an entry foreach line having a different pose than a preceding line due to cameramotion), with the first pose stored in the first line of the look-uptable.

At block 804, the eyewear device 100 captures, during a capture period,an image of an environment using the first rolling shutter camera. Theimage includes feature points and each feature point is captured at aparticular time during a capture period. The processor 432 continuouslyreceives input images from at least one visible light camera 114 andstores those images in memory 434 for processing. In some examples, theeyewear device 100 may compare objects in the captured images to objectsstored in a library of images to identify a match, e.g., for use indetermining the position of the eyewear device through visual-inertialtracking (described below). A library of images of known objects isstored in a virtual object database 484 for comparison.

At block 806, the eyewear device 100 senses movement of the mobiledevice during the capture period by obtaining motion information fromthe physical environment 600 near the device 100 from various sensors,for example, location or position information from a GPS unit 473,motion or orientation information from an IMU 472 or distanceinformation from a laser distance sensor or a combination thereof. In anexample, processor 432 retrieves sensed parameters from at least one ofthe sensors. The processor 432 then determines motion and positioninformation from the sensed parameters using techniques describedherein.

At block 808, the eyewear device 100 computes a number of poses for thefirst rolling shutter camera. The number of poses to computed by therolling shutter camera is responsive to the sensed motion of the eyeweardevice such that relatively fewer poses are computed when the eyeweardevice is moving slowly (e.g., determined based on input from a motionsensor) and relatively more poses are computed when the eyewear deviceis moving faster. In one example, the number of poses is selected basedon predefined thresholds. In accordance with this example, when theeyewear device is moving at a rate at or below a first predefinedthreshold (e.g., at or below 1 foot per second), the eyewear devicecomputes a relatively low number of poses (e.g., 3 or less) per rollingshutter cycle; when the eyewear device is moving at a rate between thefirst predefined threshold (e.g., above 1 foot per second) and a secondpredefined threshold (e.g., below 3 feet per second), the eyewear devicecomputes a medium number of poses (e.g., 4-6) per rolling shutter cycle;and when the eyewear device is moving at a rate at or above the secondpredefined threshold (e.g., at or above 3 feet per second), the eyeweardevice computes a relatively high number of poses (e.g., 7 or more) perrolling shutter cycle. By adjusting the number of poses calculatedresponsive to movement of the eyewear device, processing resources canbe conserved when they are not necessary to produce acceptable results.

To calculate each of the number of poses, the processor 432, determinesan initial pose of the eyewear device 100 within the environment andobtains movement information provided by sensor input (see block 806) tocompute a computed pose. Each computed pose corresponds to a particulartime within a capture period. In one example, the processor 432determines the pose for a line using a simultaneous localization andmapping (SLAM) algorithm applied to data received from one or moresensors for a first pose during exposure of a first line of at least oneof the rolling shutter cameras. In some examples each of the computedposes is stored by processor 432 in memory, e.g., memory 434. In oneexample, the processor 432 stores each of the computed poses in alook-up table in memory 434.

In some examples, for each feature point in the image, the one of thenumber of computed poses is retrieved from the lookup table with thecorresponding particular time that is closest to the correspondingparticular computed time. In other examples, for each feature point inthe image, the one of the number of computed poses is retrieved from thelookup table with the corresponding particular time that is immediatelyprior to the corresponding particular computed time.

In one example, where the number of poses comprises first and secondcalculated poses, the processor 432 stores, in a first position of alook-up table, the first calculated pose for a first line of the rollingshutter camera and, if the second calculated pose is calculated for asubsequent line of the first rolling shutter camera, the firstcalculated pose for the second line of the first rolling shutter camera.In one example, the number of computed poses is less than the number offeature points.

At block 810, the eyewear device selects, for each feature point in theimage, one of the number of computed poses by matching the particularcapture time for the feature point to the particular computed time forthe computed pose. At block 812, the eyewear device determines aposition of the mobile device within the environment using the featurepoints and the selected computed poses for the feature points. In oneexample, the position of the mobile device is determined by using theretrieved lookup table position poses. The first lookup table positionpose for a first feature point corresponding to the first line and thesecond lookup table position pose for a second feature pointcorresponding to the second line are retrieved from memory 434. In oneexample, determining the position comprises applying a simultaneouslocalization and mapping (SLAM) algorithm using the feature points andthe selected computed poses for the feature points.

FIGS. 8B-8D are additional flow charts 820, 830, and 840 listing stepsin example methods of augmented reality guidance experiences. Althoughthe steps are described with reference to the eyewear device 100, asdescribed herein, other implementations of the steps described, forother types of wearable mobile devices, will be understood by one ofskill in the art from the description herein. Additionally, it iscontemplated that one or more of the steps shown in FIGS. 8B-D, anddescribed herein, may be omitted, performed simultaneously or in aseries, performed in an order other than illustrated and described, orperformed in conjunction with additional steps.

In FIG. 8B, at block 822, the processor 432 stores each of the computedposes in a lookup table in memory 434. At block 824, for each featurepoint in the image, one of the number of the computed poses is retrievedfrom the lookup table with the corresponding particular time that isclosest to the corresponding particular computed time.

In FIG. 8C, at block 832, the processor 432 stores each of the computedposes in a lookup table in memory 434. At block 834, for each featurepoint in the image, one of the number of the computed poses is retrievedfrom the lookup table with the corresponding particular time that isimmediately prior to the corresponding particular computed time.

FIG. 8D is a flow chart 840 depicting a method for visual-inertialtracking on eyewear device 100 that uses a camera system comprisingfirst and second rolling shutter cameras. In one example, the camerasystem is a stereoscopic camera system. FIG. 8A illustrates steps 802through 812 performed for a first rolling shutter camera. The stepsperformed for the second rolling shutter camera are as follows.

At step 842, the eyewear device 100 obtains an initial pose for thesecond rolling shutter camera. In some examples the pose is stored byprocessor 432 in memory, e.g., memory 434. In one example, the processor432 stores the pose in a look-up table in memory 434. The processor 432may set up the look-up table in memory and maintain the look-up tableduring a visual-inertial tracking process by eyewear device 100. Thelook-up table may include an entry corresponding to each line of arolling shutter camera (or, for example, an entry for each line having adifferent pose than a preceding line due to camera motion), with thefirst pose stored in the first line of the look-up table.

At step 844, the eyewear device 100 captures, during a capture period, asecond image of an environment using the camera system. The second imageincludes feature points with each feature point being captured at aparticular capture time during the capture period. The processor 432 maycontinuously receive input images from the second visible light camera114 and store those images in memory 434 for processing. In someexamples, the eyewear device 100 may compare objects in the capturedimages to objects stored in a library of images to identify a match,e.g., for use in determining the position of the eyewear device throughvisual-inertial tracking (described below). A library of images of knownobjects is stored in a virtual object database 484 for comparison.

At block 846, the eyewear device 100 senses movement of the mobiledevice at a plurality of times during the capture period by obtainingmotion information from the physical environment 600 near the device 100from various sensors, for example, location information from a GPS unit473, orientation information from an IMU 472 or distance informationfrom a laser distance sensor. In an example, processor 432 retrievessensed parameters from at least one of GPS 473, IMU 472, a laserdistance sensor, cameras 114, or a combination thereof. The processorthen determines motion and position information from the sensedparameters using techniques described herein.

At block 848, the eyewear device 100 computes a number of poses for thesecond rolling shutter camera based on the initial pose and the sensedmovement, each computed pose corresponding to a particular computed timewithin the capture period. The number of computed poses for the secondrolling shutter camera is responsive to the sensed movement of themobile device. The number of poses to compute can be determined asdescribed above with reference to block 808. To calculate each of thenumber of poses, the processor 432, for example, determines a head pose(roll, pitch, and yaw) of the eyewear device 100 within the environmentby using motion and position information obtained from sensors (seeblock 806). In one example, the processor 432 of the eyewear device 100determines its position with respect to one or more objects 604 withinthe environment 600 using captured images, constructs a map of theenvironment 600 using a coordinate system (x, y, z) for the environment600, and determines its position within the coordinate system. Forexample, the processor 432 may determine a head pose (roll, pitch, andyaw) of the eyewear device 100 within the environment by using two ormore location points (e.g., three location points 606 a, 606 b, and 606c) associated with a single object 604 a, or by using one or morelocation points 606 associated with two or more objects 604 a, 604 b,604 c. In another example, the processor 432 determines the head poseusing other sensors (e.g., IMU 472 or GPS 473) in addition to or insteadof captured images. In one example, the processor 432 determines thepose for a line using a simultaneous localization and mapping (SLAM)algorithm applied to data received from one or more sensors for a firstpose during exposure of a first line of the second rolling shuttercamera.

At block 850, the eyewear device 100 selects, for each feature point inthe second image, one of the number of second camera computed poses bymatching the particular capture time for the feature point to theparticular computed time for the computed pose.

At block 852, the eyewear device 100 determines a position of the mobiledevice within the environment using the feature points and the selectedsecond camera computed poses for the feature points of the second image.

Any of the functionality described herein can be embodied in one morecomputer software applications or sets of programming instructions, asdescribed herein. According to some examples, “function,” “functions,”“application,” “applications,” “instruction,” “instructions,” or“programming” are program(s) that execute functions defined in theprograms. Various programming languages can be employed to implement oneor more of the applications, structured in a variety of manners, such asobject-oriented programming languages (e.g., Objective-C, Java, or C++)or procedural programming languages (e.g., C or assembly language). In aspecific example, a third-party application (e.g., an applicationdeveloped using the ANDROID™ or IOS™ software development kit (SDK) byan entity other than the vendor of the particular platform) may includemobile software running on a mobile operating system such as IOS™,ANDROID™, WINDOWS® Phone, or another mobile operating systems. In thisexample, the third-party application can invoke API calls provided bythe operating system to facilitate functionality described herein.

Hence, a machine-readable medium may take many forms of tangible storagemedium. Non-volatile storage media include, for example, optical ormagnetic disks, such as any of the storage devices in any computerdevices or the like, such as may be used to implement the client device,media gateway, transcoder, etc. shown in the drawings. Volatile storagemedia include dynamic memory, such as main memory of such a computerplatform. Tangible transmission media include coaxial cables; copperwire and fiber optics, including the wires that comprise a bus within acomputer system. Carrier-wave transmission media may take the form ofelectric or electromagnetic signals, or acoustic or light waves such asthose generated during radio frequency (RF) and infrared (IR) datacommunications. Common forms of computer-readable media thereforeinclude for example: a floppy disk, a flexible disk, hard disk, magnetictape, any other magnetic medium, a CD-ROM, DVD or DVD-ROM, any otheroptical medium, punch cards paper tape, any other physical storagemedium with patterns of holes, a RAM, a PROM and EPROM, a FLASH-EPROM,any other memory chip or cartridge, a carrier wave transporting data orinstructions, cables or links transporting such a carrier wave, or anyother medium from which a computer may read programming code or data.Many of these forms of computer readable media may be involved incarrying one or more sequences of one or more instructions to aprocessor for execution.

Except as stated immediately above, nothing that has been stated orillustrated is intended or should be interpreted to cause a dedicationof any component, step, feature, object, benefit, advantage, orequivalent to the public, regardless of whether it is or is not recitedin the claims.

It will be understood that the terms and expressions used herein havethe ordinary meaning as is accorded to such terms and expressions withrespect to their corresponding respective areas of inquiry and studyexcept where specific meanings have otherwise been set forth herein.Relational terms such as first and second and the like may be usedsolely to distinguish one entity or action from another withoutnecessarily requiring or implying any actual such relationship or orderbetween such entities or actions. The terms “comprises,” “comprising,”“includes,” “including,” or any other variation thereof, are intended tocover a non-exclusive inclusion, such that a process, method, article,or apparatus that comprises or includes a list of elements or steps doesnot include only those elements or steps but may include other elementsor steps not expressly listed or inherent to such process, method,article, or apparatus. An element preceded by “a” or “an” does not,without further constraints, preclude the existence of additionalidentical elements in the process, method, article, or apparatus thatcomprises the element.

Unless otherwise stated, any and all measurements, values, ratings,positions, magnitudes, sizes, and other specifications that are setforth in this specification, including in the claims that follow, areapproximate, not exact. Such amounts are intended to have a reasonablerange that is consistent with the functions to which they relate andwith what is customary in the art to which they pertain. For example,unless expressly stated otherwise, a parameter value or the like mayvary by as much as ±10% from the stated amount.

In addition, in the foregoing Detailed Description, it can be seen thatvarious features are grouped together in various examples for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as reflecting an intention that the claimed examplesrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, the subject matter to be protected liesin less than all features of any single disclosed example. Thus, thefollowing claims are hereby incorporated into the Detailed Description,with each claim standing on its own as a separately claimed subjectmatter.

While the foregoing has described what are considered to be the bestmode and other examples, it is understood that various modifications maybe made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that they may be appliedin numerous applications, only some of which have been described herein.It is intended by the following claims to claim any and allmodifications and variations that fall within the true scope of thepresent concepts.

What is claimed is:
 1. A method for visual-inertial tracking with amobile device having a motion detector and a camera system including afirst rolling shutter camera, the method comprising: obtaining aninitial pose for the first rolling shutter camera; capturing, during acapture period, an image of an environment using the camera system, theimage including feature points, each feature point captured at aparticular capture time during the capture period; sensing, during thecapture period, movement of the mobile device with the motion detector;computing a number of poses for the first rolling shutter camera basedon the initial pose and the sensed movement, each computed posecorresponding to a particular computed time within the capture period,wherein the number of computed poses is responsive to the sensedmovement of the mobile device, wherein the number of poses computed bythe mobile device varies with the sensed movement of the mobile device;selecting, for each feature point in the image, one of the number ofcomputed poses by matching the particular capture time for the featurepoint to the particular computed time for the computed pose, wherein thenumber of poses is selected based on predefined thresholds; anddetermining a position of the mobile device within the environment usingthe feature points and the selected computed poses for the featurepoints.
 2. The method of claim 1, further comprising: storing each ofthe computed number of poses in a lookup table; wherein the selectingincludes retrieving, for each feature point in the image, the one of thenumber of computed poses from the lookup table with the correspondingparticular capture time that is closest to the corresponding particularcomputed time.
 3. The method of claim 1, further comprising: storingeach of the computed number of poses in a lookup table; wherein theselecting includes retrieving, for each feature point in the image, theone of the number of computed poses from the lookup table with thecorresponding particular capture time that is immediately prior to thecorresponding particular computed time.
 4. The method of claim 1,wherein the camera system is a multi-camera camera system furthercomprising at least a second rolling shutter camera.
 5. The method ofclaim 4, further comprising: obtaining another initial pose for thesecond rolling shutter camera; capturing, during another capture period,a second image of the environment using the second rolling shuttercamera, the image including feature points, each feature point capturedat a particular capture time during the other capture period; sensing,at a plurality of times during the other capture period, movement of themobile device with the motion detector; computing a number of poses forthe second camera based on the initial pose and the sensed movement,each second camera computed pose corresponding to a particular computedtime within the other capture period, wherein the number of secondcamera computed poses is responsive to the sensed movement of the mobiledevice during the other capture period; selecting, for each featurepoint in the second image, one of the number of second camera computedposes by matching the particular capture time for the feature point tothe particular computed time for the computed pose; and determining theposition of the mobile device within the environment using the featurepoints for the first image, the feature points for the second image, andthe selected computed poses for the feature points.
 6. The method ofclaim 5, the method further comprising: storing each of the secondcamera computed number of poses in a lookup table; wherein the selectingincludes retrieving, for each feature point in the image, the one of thenumber of second camera computed poses from the lookup table with thecorresponding particular capture time that is closest to thecorresponding particular computed time.
 7. The method of claim 5,wherein the determining comprises: storing each of the second cameracomputed number of poses in a lookup table; wherein the selectingincludes retrieving, for each feature point in the image, the one of thenumber of second camera computed poses from the lookup table with thecorresponding particular capture time that is immediately prior to thecorresponding particular computed time.
 8. The method of claim 1,wherein the determining the position comprises applying a simultaneouslocalization and mapping (SLAM) algorithm using the feature points andthe selected computed poses for the feature points.
 9. The method ofclaim 1, wherein the sensing movement comprises at least one of: sensingmotion with an inertial measurement unit (IMU); or sensing a rate ofchange in position of the mobile device responsive to coordinates from aglobal positioning system (GPS).
 10. The method of claim 1, wherein thenumber of computed poses is less than the number of feature points. 11.A visual-inertial tracking system for determining a position of aneyewear device within an environment, the system comprising: a motiondetector; a first rolling shutter camera; an eyewear device comprisingthe motion detector, the first rolling shutter camera, a processor, anda memory; and programming in the memory, wherein execution of theprogramming by the processor configures the eyewear device to obtain aninitial pose for the first rolling shutter camera, capture, during acapture period, an image of an environment using the camera system, theimage including feature points, each feature point captured at aparticular capture time during the capture period, sense, during thecapture period, movement of the eyewear device with the motion detector,compute a number of poses for the first rolling shutter camera based onthe initial pose and the sensed movement, each computed posecorresponding to a particular computed time within the capture period,wherein the number of computed poses is responsive to the sensedmovement of the eyewear device and the number of poses computed by theeyewear device varies with the sensed movement of the eyewear device,select, for each feature point in the image, one of the number ofcomputed poses by matching the particular capture time for the featurepoint to the particular computed time for the computed pose, wherein thenumber of poses is selected based on predefined thresholds; anddetermine a position of the eyewear device within the environment usingthe feature points and the selected computed poses for the featurepoints.
 12. The system of claim 11, further comprising: a lookup tablestored in memory, wherein each of the computed number of poses is storedin the lookup table.
 13. The system of claim 12, further comprising:store, in memory, each of the computed number of poses in a lookuptable; and retrieve, from memory, for each feature point in the image,the one of the number of computed poses from the lookup table with thecorresponding particular capture time that is closest to thecorresponding particular computed time.
 14. The system of claim 12,further comprising: store, in memory, each of the computed number ofposes in a lookup table; and retrieve, from memory, for each featurepoint in the image, the one of the number of computed poses from thelookup table with the corresponding particular capture time that isimmediately prior to the corresponding particular computed time.
 15. Thesystem of claim 11, wherein the system further comprises a multi-cameracamera system comprising a second rolling shutter camera.
 16. The systemof claim 15, wherein the programming in the memory, when executed by theprocessor further configures the eyewear device to obtain anotherinitial pose for the second rolling shutter camera, capture, duringanother capture period, a second image of the environment using thesecond rolling shutter camera, the image including feature points, eachfeature point captured at a particular capture time during the othercapture period, sense, at a plurality of times during the other captureperiod, movement of the eyewear device with the motion detector, computea number of poses for the second camera based on the initial pose andthe sensed movement, each second camera computed pose corresponding to aparticular computed time within the other capture period, wherein thenumber of second camera computed poses is responsive to the sensedmovement of the eyewear device during the other capture period, select,for each feature point in the second image, one of the number of secondcamera computed poses by matching the particular capture time for thefeature point to the particular computed time for the computed pose, anddetermine the position of the eyewear device within the environmentusing the feature points for the first image, the feature points for thesecond image, and the selected computed poses for the feature points.17. The system of claim 15, wherein the programming in the memory, whenexecuted by the processor further configures the eyewear device tostore, in memory each of the second camera computed number of poses in alookup table; retrieve, from memory, for each feature point in theimage, the one of the number of second camera computed poses from thelookup table with the corresponding particular capture time that isclosest to the corresponding particular computed time.
 18. The system ofclaim 15, wherein the programming in the memory, when executed by theprocessor further configures the eyewear device to store, in memory,each of the second camera computed number of poses in a lookup table;and retrieve, from memory, for each feature point in the image, the oneof the number of second camera computed poses from the lookup table withthe corresponding particular capture time that is immediately prior tothe corresponding particular computed time.
 19. The system of claim 11,wherein the number of computed poses is less than the number of featurepoints.
 20. A non-transitory computer-readable medium storing programcode for balancing pose accuracy and computation load duringvisual-inertial tracking when executed by an eyewear device having atleast one rolling shutter camera, a processor, a memory, and a motiondetector, the program code, when executed, is operative to cause anelectronic processor to perform the steps of: obtaining an initial posefor the at least one rolling shutter camera; capturing, during a captureperiod, an image of an environment using the at least one rollingshutter camera, the image including feature points, each feature pointcaptured at a particular capture time during the capture period;sensing, during the capture period, movement of the eyewear device withthe motion detector; computing a number of poses for the at least onerolling shutter camera based on the initial pose and the sensedmovement, each computed pose corresponding to a particular computed timewithin the capture period, wherein the number of computed poses isresponsive to the sensed movement of the eyewear device, wherein thenumber of poses computed by the eyewear device varies with the sensedmovement of the eyewear device; selecting, for each feature point in theimage, one of the number of computed poses by matching the particularcapture time for the feature point to the particular computed time forthe computed pose, wherein the number of poses is selected based onpredefined thresholds; and determining a position of the eyewear devicewithin the environment using the feature points and the selectedcomputed poses for the feature points.